Hello,
Please do not ask for a save before investigating this, as it happens in every single game, and multiple people complain about it.
Very often, on the strategic map, you'll see the battle resolve, then stray projectiles will fly the wrong way, and keep going until they reach the literal edge of the map. This can sometimes take several minutes. Of waiting. Just so you can take your next turn.
Your worst enemy? Not the Drengin, the Yor, the Dread Lords, whatever. Its this bug!